In the refining of distillate and residual lubricating oil fractions by dewaxing, considerable quantities of slack wax are obtained. Depending on the type of lubricating oil fraction from which they originate these slack waxes are termed distillate slack wax or residual slack wax. The distillate slack waxes are further sub-classified, according to increasing molecular weight, as spindle oil slack wax, light machine oil slack wax and medium machine oil slack wax. Slack waxes, regardless of type, contain a considerable quantity of oil that can be removed by de-oiling. By a process of de-oiling distillate paraffin waxes are obtained from the distillate slack waxes and residual paraffin waxes from the residual slack wax.
Solid paraffin wax is used on a large scale for coating paper and cardboard, where the paraffin wax is often used in combination with polymers, and also in the manufacture of candles and polishes. In a number of applications for solid paraffin wax, particularly those mentioned above, two properties of the paraffin wax play an important role in the ease of processing the material. These two properties are (a) the molecular weight, and (b) the setting point of the paraffin wax. In general, it may be said that a solid paraffin wax is better suited to the above applications if the paraffin wax has a higher molecular weight and a higher setting point.
The molecular weight of a solid paraffin wax is largely determined by the lubricating oil fraction from which the paraffin wax originates. Higher molecular weight solid paraffin waxes are typically derived from heavier lubricating oil fractions. Consequently, residual paraffin wax generally has a higher molecular weight than distillate paraffin wax and the molecular weight of distillate paraffin wax increases going from spindle oil paraffin wax to medium machine oil paraffin wax. For the setting point of a solid paraffin wax such general criteria are not available since the setting point greatly depends on the structure of the paraffin wax.
It is broadly known to treat waxes with oxidizing agents to modify the properties of the wax or to convert the wax to products of different character. For example, Ludecke, U.S. Pat. No. 901,718 teaches that oils, fats, waxes and the like can be bleached by contact with peroxides. A similar process of bleaching wax by contact with peroxides employed in combination with an oxidizing gas is disclosed in Swiss Pat. No. 280,480. Merely et al, U.S. Pat. No. 2,626,277, describe a process of producing oxygenated reaction products by treating waxes with peroxides and air. A published German application, OLS No. 2,361,652, discloses the production of lubricating oils by contacting mineral oil fractions with organic peroxides. The resulting lubricants do not require the presence of polymeric VI improvers, probably because of the presence of species of increased molecular weight. None of these references recognize the need for increasing the molecular weight of solid paraffin waxes in order to obtain improved properties, or how to achieve such a result.
With regard to solid paraffin wax obtained from typical lubricating oil fractions, it has been found that the paraffin waxes generally have a sufficiently high setting point, but that, especially for the solid paraffin wax originating from the lighter lubricating oil fractions, a higher molecular weight is desirable. Consequently, there is a need for a process offering the possibility of increasing the molecular weight of a solid paraffin wax by a simple procedure. However, such a process can only be useful if the original high setting point of the paraffin wax is maintained, or perhaps even increased, but in any event, is not decreased by more than about 5.degree. C.